It has long been recognized that drinking cups and other nestable containers with superior properties, especially for the retention of hot beverages such as coffee, can be formed from expanded thermoplastic materials, the most popular of which has proven to be expanded polystyrene. A very popular cup of this type is a one-piece cup which is molded directly from expandable polystyrene beads in a steam chest. However, in forming cups in this manner, it has proven to be necessary, for purposes of imparting adequate strength, rigidity and liquid impermeability to the sidewall thereof, to construct such cups with a thick sidewall, at least in relationship to the sidewall thickness to other types of insulated cups. As a consequence of this added sidewall thickness, it is not possible to obtain as small a stacking height, or spacing, between like cups in a nested stack thereof, with the result that such cups require considerably more storage space than a comparable quantity of other types of nestable insulating cups. Another disadvantage of the so called steam chest molded cup is that, as an inherent consequence of its mode of manufacture, the external surface of its sidewall can only be decorated by post decorating or printing techniques which are slower and more expensive than the flexographic and other sheet printing techniques which may be used in decorating cups fabricated from pre-printed sheet. As a result, the vast majority of such steam chest molded cups which appear in the market place do not contain a decorated or printed outer surface.
Another known type of insulated or expanded thermoplastic drinking cup which has enjoyed some measure of commercial popularity is a two-piece cup such as that which is manufactured and marketed by the assignee of this application under the trademark "X-Fome" and which corresponds to the cup described in U.S. Pat. No. 3,468,467 which is assigned to the assignee of this application. The sidewall of such cup may be formed by conventional cup fabricating techniques from a crescent-shaped blank of an expanded plastic material which, in turn, is cut from a pre-printed sheet or web of indefinite length thereof. By controlling the density of such sheet, it is possible to fabricate a cup with adequate strength, rigidity and liquid impermeability and which, nonetheless, has a considerably thinner sidewall than a steam chest molded cup for superior stacking or nesting properties in relationship thereto. Also, the ease with which the exterior of the sidewall of such cups can be provided with attractive decoration by pre-decorating the sheet from which the sidewall blanks are formed, has made it possible for a substantial portion of such cups to be decorated in a way which has proven to be quite popular in the trade. One of the drawbacks of such a cup is its costliness, at least insofar as material costs are concerned, in relationship to the steam chest molded cup, due in part to the scrap which is inherently formed when a crescent shaped sidewall blank is cut from a sheet or web of normal character.
Yet another known type of insulated or expanded thermoplastic drinking cup which has also enjoyed some measure of commercial popularity is a one-piece, seamless deep drawn cup which is manufactured and marketed by the assignee of this application and which corresponds to the cup described in U.S. Pat. No. 3,666,162, issued May 30, 1972 (J. R. Tiffin et al). Such cups can, in somewhat higher densities than conventional steam chest molded cups, be formed to very close manufacturing tolerances and with very low stacking height, and because of these features, they have, in spite of somewhat more costliness than the steam chest molded cup and the two-piece cup described above, and in spite of the fact that they can only be decorated after forming, gained a substantial measure of popularity in the coin-operated beverage vending machine market.